This invention relates to a comminuting device including a cylinder jacket which surrounds a cylindrical comminuting chamber. In the comminuting chamber several rotors are driven and can be operated independently of one another via shafts which are concentric to one another. The rotors are arranged concentrically to the central axis of the comminuting chamber. The concentric shafts encompass a central shaft and at least one outer hollow shaft which surround the latter. One such comminuting device is known for example from German Patent No. DE 10 2013 110 352 A. As in this invention, striking tools are connected to at least two of the rotors. One of the rotors can be a fan rotor. When materials are being comminuted, shards and dust form which can adversely affect the bearings of the coaxial shafts or can reduce their service life.